cousin vs first cousin

cousin and first cousin both are nouns.

Word	Noun	Adjective	Verb	Adverb
cousin	Yes	No	No	No
first cousin	Yes	No	No	No

As nouns, cousin and first cousin are synonyms defined as:

Other synonyms of cousin include cousin-german, full cousin.

cousin (noun)	first cousin (noun)
the child of your aunt or uncle	the child of your aunt or uncle